Breastfeeding has evolved as the optimal survival strategy for human infants, especially under adverse environmental conditions. The protective benefits of breast milk are many, including the actions of bioactive components in milk that orchestrate the maturation of the gut. Infants in rural Gambia show growth patterns typical of low-income countries - low birthweight and modest catch-up, followed by precipitous growth failure - but with an additional modulation by season of the year, with extremely poor growth during the wet, or 'hungry' season. Using results from a longitudinal analysis of milk composition, infant growth, and maternal and infant health, I discuss how breast milk bioactive components shape infant growth patterns across seasons, and across generations.